A strain of an animal exists in wild in which there is only one nucleolus in the nucleus of each cell instead of the usual two.
When such animals are mated, approximately one quarter of the offspring have two nucleoli per nucleus, one half have one nucleolus per nucleus and one quarter have no nucleolus at all. Offspring without nucleoli die about four days after hatching.
These offspring die because they do not possess

Options

A. Mitochondria and are unable to obtain energy
B. Centrioles and are unable to undergo cell division
C. Golgi apparatus and are unable to remove dead cells
D. Ribosomes and are unable to manufacture proteins.

Answer

To solve the question regarding the offspring of the animal strain with nucleoli variations, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Problem**:
- We have a strain of animals with variations in the number of nucleoli in their cells. The offspring from mating these animals show three different phenotypes:
- 1/4 have two nucleoli,
- 1/2 have one nucleolus,
- 1/4 have no nucleolus.
- Offspring without nucleoli die shortly after hatching.

**Hint**: Identify the genetic inheritance pattern and the significance of nucleoli in cellular function.

2. **Analyzing the Offspring**:
- The offspring with no nucleoli are dying about four days after hatching. This suggests that the absence of nucleoli is critical for their survival.
- Nucleoli are involved in the production of ribosomes, which are essential for protein synthesis.

**Hint**: Consider what cellular structures are produced in the nucleolus and their importance in the cell.

3. **Identifying the Function of Ribosomes**:
- Ribosomes are responsible for translating mRNA into proteins. Without ribosomes, cells cannot synthesize proteins, which are crucial for various cellular functions, including growth, repair, and metabolism.

**Hint**: Recall the role of ribosomes in the process of translation and protein synthesis.

4. **Connecting the Dots**:
- Since the offspring without nucleoli cannot produce ribosomes, they are unable to manufacture proteins. This lack of proteins would lead to their inability to survive, explaining why they die shortly after hatching.

**Hint**: Think about the consequences of protein deficiency in living organisms.

5. **Conclusion**:
- The correct answer to the question is that the offspring without nucleoli die because they do not possess ribosomes and are unable to manufacture proteins.

**Final Answer**: D. Ribosomes and are unable to manufacture proteins.